Sulfur hexafluoride (SF6) gas or Ar/SF6 mixing gas is widely used in plasma processes. However, there are a little experimental studies with various external parameters such as gas pressure and mixing ratio. In this work, a study of the plasma parameters by changing the gas mixing ratio was done in an Ar/SF6 inductively coupled plasma from the measurement of the electron energy distribution function. At a low gas pressure, as the mixing ratio of SF6 gas increased at a fixed inductively coupled plasma (ICP) power, the electron density decreased and the electron temperature increased, while they were not changed drastically. At a high gas pressure, a remarkable increase in the electron temperature was observed with the decrease in the electron density. These variations are due to the electron loss reactions such as the electron attachment. It was also found that at a fixed ICP power, the negative ion creation with the diluted SF6 gas can change the discharge mode transition from an inductive mode to a capacitive mode at the high gas pressure. The electron attachment reactions remove the low energy electrons and change the mean electron energy towards higher energies with diluting SF6 gas at high pressure. The measured results were compared with the simplified global model, and the global model is in relatively good agreement with the measured plasma parameters except for the result in the case of the large portion of SF6 gas at the high pressure and the capacitive mode, which causes strong negative ion formation by the electron attachment reactions.
Objective To compare the perioperative outcomes of transumbilical morcellation (TUM) and transvaginal morcellation (TVM) of a large uterus (≥500 g) during single-port-access total laparoscopic hysterectomy (SPA-TLH). Methods A total of 57 patients who underwent SPA-TLH for a large uterine myoma and/or adenomyosis (uterine weight ≥500 g) between March 2013 and July 2017 were included. For specimen retrieval, TUM was performed for 30 patients and TVM for 27 patients. Results Perioperative outcomes, including total operative time, tissue extraction time, extension of skin incision length, estimated volume of blood loss, changes in postoperative hemoglobin level, length of postoperative hospital stay, postoperative pain, and uterine weight, were compared between the 2 groups. No significant differences were observed in the baseline characteristics except for a history of cesarean section (TUM vs. TVM: 83.3% vs. 14.8%, P=0.002) and history of vaginal delivery (TUM vs. TVM: 6.7% vs. 88.8%, P=0.001). The total operative time, tissue extraction time, extension of skin incision length, estimated volume of blood loss, changes in postoperative hemoglobin level, length of postoperative hospital stay, and postoperative pain did not significantly differ between the two groups. The uterine weight was significantly higher for patients who underwent TUM than for those who had TVM (median [range]: 735 g [520-1,380 g] vs. 622 g [514-975 g]; P=0.042). Conclusion TUM during SPA-TLH is a feasible technique for extracting large uteri weighing ≥500 g. This procedure is suitable for patients without a history of vaginal delivery or a narrow vaginal cavity.
A radio frequency (rf) compensation design using auxiliary double probes connected in parallel with a main measurement probe was developed for Langmuir probe diagnostics. This probe structure can reduce the sheath impedance of the main probe. In our probe design, the sheath capacitance of the probe can be increased and its sheath resistance can be decreased with increasing dc bias differential voltage between the auxiliary double probes. The I-V characteristic curve and electron energy distribution functions measured by our probe system had sufficient rf compensation performance in inductively coupled plasmas.
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